SW: add thin-provisioning-tools to GRML_FULL

Quoting from the bugreport:

| In order to activate lvm volumes which use lvm caching,
| /usr/sbin/cache_check (provided by thin-provisioning-tools) needs
| to be installed (see https://bugs.debian.org/773731). As grml
| currently does not include thin-provisioning-tools, volumes which
| use caching cannot be activated on startup (e.g. via the lvm boot
| option), not activated manually (naturally one can install
| thin-provisioning-tools via apt, but that doesn't help with
| activating on startup).

Closes grml/grml#81
Thanks: James Tocknell